Dutch ecologist Roxina Soler and her colleagues have discovered that
subterranean and aboveground herbivorous insects can communicate with
each other by using plants as telephones. Subterranean insects issue
chemical warning signals via the leaves of the plant. This way,
aboveground insects are alerted that the plant is already â€˜occupiedâ€™.

Aboveground, leaf-eating insects prefer plants that have not yet
been occupied by subterranean root-eating insects. Subterranean insects
emit chemical signals via the leaves of the plant, which warn the
aboveground insects about their presence. This messaging enables
spatially-separated insects to avoid each other, so that they do not
unintentionally compete for the same plant.

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In recent years it has been discovered that different types of
aboveground insects develop slowly if they feed on plants that also
have subterranean residents and vice versa. It seems that a mechanism
has developed via natural selection, which enables the subterranean and
aboveground insects to detect each other. This avoids unnecessary
competition.

Green telephone lines

Via the 'green telephone lines', subterranean insects can also
communicate with a third party, namely the natural enemy of
caterpillars. Parasitic wasps lay their eggs inside aboveground
insects. The wasps also benefit from the volatile signals emitted by
the leaves, as these reveal where they can find a good host for their
eggs. The communication between subterranean and aboveground insects
has only been studied in a few systems. It is still not clear how
widespread this phenomenon is.

This research was carried out at the Netherlands Institute for
Ecology (NIOO-KNAW) by Roxina Soler, Jeffrey Harvey, Martijn Bezemer,
Wim van der Putten and Louise Vet. The PhD project, in which this study
was carried out, was funded by the Free Competition of NWO Earth and
Life Sciences.